Laminated films obtained by heat-sealing or laminating a sealant film to a biaxially stretched film as a substrate film have been heretofore used in many of distribution commodities represented by food products, pharmaceutical products and industrial products. The innermost layer of a packaging material that forms packaging bags, lids and so on is provided with a sealant layer formed of a polyolefin resin such as polyethylene or polypropylene, or a copolymer resin such as ionomer, EMMA which exhibit high heat-sealing strength. These resins are known to be capable of achieving a high adhesive strength through heat-sealing, and easily adsorb various organic compounds.
An unstretched sealant film formed of a polyolefin resin as described in Patent Document 1 has excellent heat-sealing strength between polyolefin films. However, it has the disadvantage that heat-sealing strength with an unstretched polyester film and a biaxially stretched polyester film is low. A packaging material including a sealant layer formed of a polyolefin resin as the innermost layer, i.e. a layer that is in contact with the contents, has the disadvantage that it easily adsorbs oil and fat components and perfume components, so that the aroma and taste of the contents are easily changed. Some of components in the contents are unsuitable for packaging of chemical products, pharmaceutical products, food products and the like which contain organic compounds as effective components.
A packaging material including a sealant layer formed of an acrylonitrile resin as described in Patent Document 2 as the innermost layer, i.e. a layer that is in contact with the contents is suitable for packaging of chemical products, pharmaceutical products and food products which contain organic compounds as effective components. However, there is the disadvantage that the heat seal temperature must be increased for heat-sealing acrylonitrile films to each other. Further, there is the disadvantage that the heat-sealing strength with an unstretched polyester film and a biaxially stretched polyester film is low as in the case of the film in Patent Document 1.